Arrays in JavaScript

An array can hold multiple values at a time.

To create an array in JavaScript:
Create an Array in JavaScript by assigning it to square brackets

let  myArray = [];

Assigning values to Array in JavaScript

let myArray = [1, 2, 3]; 
//Access the values of Array
console.log(myArray[0]); // The output is: 1
console.log(myArray[1]); // The output is: 2 
console.log(myArray[2]); // The output is : 3
console.log(myArray[3]); // The output is: undefined

Use length to get the number of elements in an Array

The length property returns the number of elements in an Array.

let myArray = [1, 2, 3];  
console.log( myArray.length ); // The output is 3

Push Method to add elements to Array

To add an element to an Array use the push method.

let myArray = [];
myArray.push(4);
console.log( myArray );
//The output is : [4]

Pop Method: Remove the last element from the Array

The pop method removes the last element from the Array and returns that element.

let myArray = [1,2,3];
let lastElement = myArray.pop();
console.log( lastElement );
//The output is : 3

Shift Method: Removes and returns the first element from the Array

let myArray = [1,2,3];
let firstElement = myArray.shift();
console.log( firstElement );
//The output is : 1 

Splice Method: Removes elements from the Array from the index number specified

let myArray = [1,2,3,4];
myArray.splice(3,1);
console.log( myArray );
//The output is : [1,2,3]

Note: 1 here indicates how may numbers to be deleted after the index number specified.

Splice method can also add elements to an Array.

let myArray = [1,2,3,4];
myArray.splice(3,1,5,6,7); 
console.log( myArray );
//The output is: [1,2,3,5,6,7] 

Here element at index number 3 is deleted. The number of elements to be deleted is 1. So in the above myArray 4 is deleted. The elements 5,6,7 is then added to the array.

Below is the list of all the methods and properties of an Array.

3 Array Properties

constructor Function to create Array’s objects
length Gives you the number of elements in an array
prototype You can add properties and methods to an Array object using prototype

30 Array Methods
concat() Joins two or more arrays, and return the joined array
copyWithin() To copy array elements within the array, to and from specified positions
entries() Returns Array Iteration Object
every() Checks applied to every element in an array to pass a test
fill() Fill array with a static value
filter() Creates a new array with some check applied
find() Returns first element in an array to comply with check
findIndex() Returns index of first element to comply with check
forEach() Call a function for each array element
from() Get array from an object
includes() Checks if an array contains the specified element
indexOf() Returns index position of the specified element
isArray() To check if object is an Array or not
join() Joins all elements of an array and create a string
keys() Returns an Array with the keys of the original array
lastIndexOf() Return index of the specified element startin from the last
map() A new array is created with the result of calling a function for each array element
pop() Removes the last element from array, and returns that element
push() Adds an element to the end of an array, and returns the new length
reduce() Reduces to a single value (going left-to-right)
reduceRight() Reduce to a single value (going right-to-left)
reverse() Reverse the order of elements
shift() Removes first element of array, and return that element
slice() Reoves or adds a part of an array, and returns the new array
some() Checks if any of the elements in an array complies with a test
sort() Sort array elements
splice() Adds/Removes array elements
toString() Converts array elements to string
unshift() Add elements to the beginning of array, and return the new length
valueOf() Gets the primitive value of an array

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